title: Rh-catalyzed aldehyde-aldehyde cross-aldol reaction under base-free conditions: in situ aldehyde-derived enolate formation through orthogonal activation.
abstract: The chemoselective generation of aldehyde-derived enolates to realize an aldehyde-aldehyde cross-aldol reaction is described. A combined Rh/dippf system efficiently promoted the isomerization/aldol sequence by using primary allylic, homoallylic, and bishomoallylic alcohols; secondary allylic and homoallylic alcohols; and trialkoxyboranes that were derived from primary allylic and homoallylic alcohols. The reaction proceeded at ambient temperature under base-free conditions, thus giving cross-aldol products with high chemoselectivity. Mechanistic studies, as well as its application to double-aldol processes under protecting-group-free conditions, are also described.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan), Fax: (+81) 3-5684-5206; Kanai Life Science Catalysis Project, ERATO, Japan Science and Technology Agency, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan).
authors.forename: Luqing
authors.initials: L
authors.lastname: Lin
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Motomu
authors.initials: M
authors.lastname: Kanai
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry*
chemical_list: D000438:Alcohols; D000447:Aldehydes; D009942:Organometallic Compounds; D012238:Rhodium
keywords: aldol reaction; boron; homogeneous catalysis; rhodium; synthetic methods